Method of coordinating and stabilizing the delivery of wind generated energy

ABSTRACT

The invention relates to a method of coordinating and stabilizing the delivery of wind generated power, such as to a power grid, or a facility having pneumatically driven equipment, so as to avoid sudden surges and spikes, despite wind speed fluctuations and oscillations. The method preferably uses a plurality of windmill stations, wherein energy can be used directly, and/or stored for later use when demand is high or wind availability is low. The method contemplates forming an energy delivery schedule, to coordinate the use of energy from storage, based on daily wind speed forecasts, which help to predict the resulting wind power availability levels for the upcoming day. The schedule preferably sets a reduced number of constant power output periods during the day, during which time energy delivery levels remain substantially constant, despite fluctuations and oscillations in wind speed and wind power availability levels.

RELATED APPLICATIONS

This application claims priority from U.S. application Ser. No.11/242,378, filed Oct. 3, 2005, which claims priority from U.S.application Ser. No. 10/865,865, filed Jun. 14, 2004, which claimspriority from U.S. Provisional Application No. 60/478,220, filed on Jun.13, 2003.

This application claims priority from U.S. application Ser. No.11/407,733, filed on Apr. 20, 2006, which claims priority from U.S.Provisional Application Ser. No. 60/763,577, filed on Jan. 31, 2006, andfrom U.S. application Ser. No. 10/857,009, filed Jun. 1, 2004, whichclaims priority from U.S. Provisional Application Ser. No. 60/474,551,filed on May 30, 2003.

Each of these applications is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method of coordinating andstabilizing the delivery of stored energy, such as wind generated energystored in the form of compressed air energy.

BACKGROUND OF THE INVENTION

Generation of energy from natural sources, such as sun and wind, hasbeen an important objective in this country over the last severaldecades. Attempts to reduce reliance on oil, such as from foreignsources, have become an important national issue. Energy experts fearthat some of these resources, including oil, gas and coal, may somedayrun out. Because of these concerns, many projects have been initiated inan attempt to harness energy derived from what are called natural“alternative” sources.

While solar power may be the most widely known alternative source, thereis also the potential for harnessing tremendous energy from the wind.Wind farms, for example, have been built in many areas of the countrywhere the wind naturally blows. In many of these applications, a largenumber of windmills are built and “aimed” toward the wind. As the windblows against the windmills, rotational power is created and then usedto drive generators, which in turn, can generate electricity. Thisenergy is often used to supplement energy produced by utility powerplants and distributed by electrical power grids.

Wind farms are best operated when wind conditions are relativelyconstant and predictable. Such conditions enable a consistent andpredictable amount of energy to be generated and supplied, therebyavoiding surges and swings that could adversely affect the system. Thedifficulty, however, is that wind by its very nature is unpredictableand uncertain. In most cases, wind speeds, frequencies and durationsvary considerably, i.e., the wind never blows at the same speed over anextended period of time, and wind speeds themselves can varysignificantly from one moment to another. And, because the amount ofpower generated by wind is mathematically a function of the cube of thewind speed, even the slightest fluctuation or oscillation in wind speedcan result in a disproportionate change in wind-generated power. Forexample, a three-fold change in wind speed (increase or decrease) canresult in a twenty-seven-fold change in wind-generated power, i.e., 3cubed equals 27.

This is particularly significant in the context of a wind farmdelivering energy to an electrical power grid, which is a giant networkcomposed of a multitude of smaller networks. These sudden surges in onearea can upset other areas and can even bring down the entire system insome cases. Because of these problems, in current systems, wind farmpower outputs are often difficult to deal with and can cause problemsfor the entire system.

Another problem associated with wind fluctuations and oscillationsrelates to the peak power sensitivity of the transmission lines in thegrid. When wind speed fluctuations are significant, and substantial windpower output fluctuations occur, the system must be designed to accountfor these variances, so that the system will have enough power linecapacity to withstand the power fluctuations and oscillations. At thesame time, if too much consideration is given to these peak poweroutputs, the system may end up being significantly over-designed, i.e.,if the system is designed to withstand surges during a small percentageof the time, the power grid capacity during the greater percentage ofthe time may not be used efficiently and effectively.

Another related problem is the temporary loss of wind power associatedwith an absence of wind or very low wind speed in some circumstances.When this occurs, there may be a gap in wind power supply, which can bedetrimental to the overall grid power output. This is especiallyimportant when large wind farms are used, wherein greater reliance onwind-generated power, to offset peak demand periods exists.

Because of these problems, attempts have been made in the past to storeenergy produced by the wind so that wind generated energy can be usedduring peak demand periods, and/or periods when little or no wind isavailable, i.e., time-shifting the energy from when it is most availableto when it is most needed. Nevertheless, these past systems have failedto be implemented in a reliable and consistent manner. Past attemptshave not been able to reduce the inefficiencies and difficulties, aswell as the fluctuation and oscillation problems discussed above,inherent in using wind as an energy source for an extended period oftime.

Notwithstanding these problems, because wind is a significant naturalresource that will never run out, and is often in abundance in manylocations throughout the world, there is a desire to develop a method ofharnessing power generated by wind, to provide power in a manner thatallows not only energy to be stored, but enables the delivery of theenergy to the user or grid to be coordinated, managed and stabilized, tosmooth wind power fluctuations and oscillations, while at the same time,filling in wind energy gaps prior to delivery, such that energy swingsand surges that can adversely affect the user or grid can be eliminated.

SUMMARY OF THE INVENTION

The present invention relates to a method of using and storing windgenerated energy and effectively coordinating, managing and stabilizingthe delivery of that energy in a manner that enables wind powerfluctuations and oscillations to be reduced or avoided, by smoothing andstabilizing the delivery of power to the user or grid, and avoidingsudden surges and swings which can adversely affect the power deliverysystem. The present method generally comprises a process that utilizesdaily wind forecasts and projections to anticipate the wind conditionsand characteristics for the upcoming day, and then using that data toeffectively plan and develop a delivery schedule, with the objective ofenabling the system to provide the longest possible periods of timewhere wind generated power output levels to the user or grid can remainsubstantially constant, such as for the upcoming 24 hour period. In thisrespect, the present system contemplates using various types of energygenerating systems, including those that can store energy for later use,and control systems that can determine how much energy is stored and howmuch is being used from storage at any given time.

In one embodiment, the present system preferably comprises windmillstations that are dedicated to various uses. The first of these stationsis preferably dedicated to generating energy for direct and immediateuse by the end user or grid (hereinafter referred to as “immediate usestations”). The second of these windmill stations is preferablydedicated to energy storage such as by using a compressed air energysystem (hereinafter referred to as “energy storage stations”). The thirdof these windmill stations can preferably be switched between the two(hereinafter referred to as “hybrid stations”). The invention canconsist of one or more of these types.

The system is preferably designed with a predetermined number and ratioof each type of windmill station to enable the system to be botheconomical and energy efficient in generating the appropriate amount ofenergy for both immediate use and storage at any given time. In thisrespect, the present application incorporates by reference U.S.application Ser. No. 10/263,848, filed Oct. 4, 2002, in its entirety.These systems are preferably used in communities or facilities wherethere is a need for a large number of windmill stations, i.e., a windfarm, and/or access to an existing power grid, such that energy from thesystem can be used to supplement conventional energy sources. Thepresent application also incorporates by reference U.S. application Ser.No. 10/857,009, filed Jun. 1, 2004, in its entirety. These systems arepreferably used in circumstances where wind farms are located far fromthe end user community or facility or power grid in need of the energy,wherein the energy can be stored as compressed air within a pipelinesystem extending from the wind farm to the user or grid.

Each immediate use station preferably has a horizontal axis wind turbine(HAWT) and an electrical generator located in the nacelle of thewindmill, such that the rotational movement caused by the wind isdirectly converted to electrical energy via the generator. This can bedone, for example, by directly connecting the electrical generator tothe rotational shaft of the wind turbine so that the mechanical powerderived from the wind can directly drive the generator. By locating thegenerator downstream from the gearbox on the windmill shaft, and byusing the mechanical power of the windmill directly, energy lossestypically attributed to other types of arrangements can be avoided. Animmediate use station can also be adapted to supply energy in otherforms, such as compressed air, i.e., to drive pneumatic tools anddevices.

The energy storage stations are more complex in terms of bringing themechanical rotational energy from the above ground nacelle down toground level as rotational mechanical energy. When compressed airsystems are used, each energy storage station is preferably connected toa compressor in a manner that converts wind power to compressed airenergy directly. The horizontally oriented wind turbine of each energystorage station can be adapted to have a horizontal shaft connected to afirst gear box, which is connected to a vertical shaft extending downthe windmill tower, which in turn, is connected to a second gear boxconnected to another horizontal shaft located on the ground. The lowerhorizontal shaft can then be connected to the compressor, such that themechanical power derived from the wind can be converted directly tocompressed air energy and stored. In another embodiment, the compressorcan be located in the nacelle of the wind turbine, and a compressed airenergy storage pipe can be extended down the tower, wherein thecompressed air energy can be transferred down the wind turbine to thestorage means, whether a tank or extended pipeline, on the ground, aswill be discussed.

The compressed air from each energy storage station is preferablychanneled into one or more high-pressure storage tanks or pipelinesystems, as described in U.S. application Ser. No. 10/857,009, where thecompressed air can be stored. Storage of compressed air allows theenergy derived from the wind to be stored for an extended period oftime. By storing energy in this fashion, the compressed air can bereleased and expanded by turbo expanders at the appropriate time, suchas when little or no wind is available, and/or during peak demandperiods. The released and expanded air can then drive an electricalgenerator, such that energy derived from the wind can be used togenerate electrical power on an “as needed” basis, i.e., when the poweris actually needed, which may or may not coincide with when the windactually blows. The energy storage stations can be adapted to supplyenergy in other forms, such as compressed air energy, i.e., to drivepneumatic tools and devices, wherein, in such case, the compressed airenergy in storage would not have to be converted into electricity first,which can help increase the efficiency of the system.

The present invention contemplates that the storage tank, pipelinesystem, and/or related components, and their masses, can be designed toabsorb and release heat to maintain the stored compressed air at arelatively stable temperature, even during compression and expansion.For example, when large storage tanks are used, the preferred embodimentcomprises using a heat transfer system made of tubing extending throughthe inside of each tank, wherein heat transfer fluid (such as anantifreeze) can be distributed through the tubing to provide acost-efficient way to keep the temperature in the tank relativelystable.

The present system can also incorporate other heating systems, includingheating devices that can be provided with the storage tanks that canhelp generate additional heat and pressure, and provide a means by whichthe expanding air can be prevented from freezing. Alternatively, thepresent invention also contemplates using a combination of solar heat,waste heat from the compressor, combustors, and low level fossil fuelpower, etc., to provide the necessary heat to increase the temperatureand pressure of the compressed air in the storage tank or pipeline. Thepipeline, for example, can be laid out on the desert floor and paintedblack, which allows energy from the sun to be absorbed more efficiently.

The present system also contemplates that the cold air created by theexpansion of the compressed air exhausting from the turbo-expander canbe used for additional refrigeration purposes, i.e., such as during thesummer where air conditioning services might be in demand. Other energystorage means, such as conventional batteries, hydraulic pressure heads,etc., can also be used in connection with the present invention.

It can be seen that the immediate use stations discussed above can beused to produce electricity directly from the windmill stations forimmediate delivery to the user or power grid. On the other hand, it canbe seen that the energy storage stations can be used to time shift thedelivery of wind generated power, so that wind generated power can bemade available to the user or power grid even at times that are notcoincident with when the wind actually blows, i.e., even when little orno wind is blowing, and/or during peak demand periods. The coordinationand usage of these stations enables the current system to providecontinuous and uninterrupted power in a stabilized manner to the user orpower grid, despite fluctuations and oscillations in wind speed, bycoordinating and managing the flow of energy from the various stations.

The present system can also incorporate hybrid windmill stations thatcan be customized and switched between energy for immediate use, andenergy for storage, i.e., a switch can be used to determine the levelsof energy dedicated for immediate use and storage. In such case, theratio between the amount of energy dedicated for immediate use and theamount dedicated for storage can be further changed by making certainadjustments, i.e., such as by using clutches and gears located on thehybrid station, so that the appropriate amount of energy of each kindcan be provided. This enables the hybrid station to be customized to agiven application at virtually any time, to allow the system to providethe appropriate amount of power for immediate use and energy storage,depending on wind availability and energy demand at any given moment. Inone embodiment, the system can be comprised of all hybrid windmillstations, with the ability to switch between providing energy forimmediate use and energy storage.

Using these types of windmill stations, the present system is betterable to allocate wind-generated energy to either immediate delivery tothe user or grid, or energy storage and usage, depending on the windconditions and needs. For example, the hybrid stations can be used inconjunction with the immediate use and energy storage stations toprovide the proper ratio of power which would enable large wind farms tobe designed in a more flexible and customized manner, e.g., so that theappropriate amount of energy can be delivered to the user or grid at theappropriate time to meet the particular demands of the system. In short,using a combination of the different types of windmill stations enablesa system to be more specifically adapted and customized so that aconstant supply of power can be provided for longer periods of time.

The wind patterns in any particular location can change from time totime, i.e., from one season to another, from one month to another, and,most importantly, from day to day, hour to hour, and minute to minute.Accordingly, these fluctuations and oscillations must be dealt with inconjunction with energy storage for the system to provide continuouspower at a more constant rate. For this reason, the present inventioncontemplates that daily wind forecasts can be obtained for theparticular area where the windmill stations are located, to project thewind conditions and characteristics for each upcoming period of time,such as the next day or 24 hour period. These wind forecasts areintended to be based on the latest weather forecast technologiesavailable to approximate as closely as possible the actual expected windconditions over the course of the upcoming period, and used to forecastor predict the amount of power that could be generated by the windduring those times. While these forecasts may not be entirely accurate,they can provide a very close approximation of the expected windconditions, sufficient for purposes of planning and developing the winddelivery schedules that will enable the system to continually operate.

Once each daily forecast is obtained, the present method preferablycontemplates using the data to formulate an energy delivery schedule forthe upcoming period, based on the forecast or prediction, with theobjective of creating the longest possible periods of time during whichthe wind generated power output level to the user or grid can remainsubstantially constant. For example, in the preferred embodiment, it isdesirable to have no more than about three constant power output periodsduring any given day, such that there would be less than three changesin the rate of power being supplied to the user or grid on any given day(although up to as many as 7 or so constant power periods can beprovided if necessary). By enabling the system to provide longer periodswhen the wind generated power output is substantially constant, andfewer changes in the amount of the power output, the present systemenables power surges and swings, such as those caused by wind speedfluctuations and oscillations, to be reduced and in some caseseliminated altogether.

The manner in which the daily schedules are planned and carried outpreferably utilizes the windmill stations discussed above, as well as avalve control system for controlling the amount of energy that is storedand used from storage. The system contemplates being able to control theamount of wind generated power output levels at any given time byimplementing an appropriate number of immediate use and energy storagestations for generating energy, and/or by converting the appropriatenumber of hybrid stations, and then controlling how much energy issupplied directly, and how much is provided via energy storage, usingcompressors and expanders, at any given moment in time. The controls arealso necessary to maintain proper levels of energy in storage, based oncontinually updating the wind forecasts, so that the system never runsout of stored energy. Based on wind forecasts, it is possible during anygiven day to anticipate the need for additional energy in storage (suchas when it is expected that the power needed may exceed the powersupplied during the upcoming 24 hour period), and when it is not needed(such as when it is expected that there will be sufficient wind toprovide direct energy during the next 24 hour period).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a shows a flow-chart of a horizontal axis wind turbine system ofthe present invention dedicated to generating energy for immediate use;

FIG. 1 b shows a flow-chart of a modified horizontal axis wind turbinesystem of the present invention dedicated to storing energy in acompressed air energy system;

FIG. 2 a shows a flow-chart of a hybrid horizontal axis wind turbinesystem of the present invention for generating electricity betweenimmediate use and energy storage;

FIG. 2 b shows an example of a pressure release valve system of thepresent invention;

FIG. 3 shows a wind histogram for a location in Kansas during the monthof November 1996;

FIG. 4 shows six daily wind histories for the period between Nov. 1 andNov. 6, 1996 at the same Kansas site;

FIG. 5 shows a comparison between the Nordex N50/800 and a computermodel;

FIG. 6 contains two charts showing two potential delivery schedules forNov. 1, 1996;

FIG. 7 a contains two charts showing an 87/13 ratio between immediateuse and energy storage, the top chart comparing the constant outputperiods with the wind/power availability curve, and the bottom chartcomparing the constant output periods with the amount of power suppliedinto storage, both for the same Nov. 1, 1996 day;

FIG. 7 b contains two charts, the top chart showing the amount of energyin storage over time, and the bottom chart showing the pressure andtemperature curves in storage, both for the same Nov. 1, 1996 day;

FIG. 8 a contains two charts for Nov. 5, 1996 at the same site showing a60/40 ratio between immediate use and energy storage, the top chartcomparing the constant output periods with the wind/power availabilitycurve, and the bottom chart comparing the constant output periods withthe amount of power supplied into storage;

FIG. 8 b contains two charts for Nov. 5, 1996, the top chart showing theamount of energy in storage over time, and the bottom chart showing thepressure and temperature curves in storage;

FIG. 9 a contains two charts for Nov. 6, 1996 at the same site showing a50/50 ratio between immediate use and energy storage, the top chartcomparing the constant output periods with the wind/power availabilitycurve, and the bottom chart comparing the constant output periods withthe amount of power supplied into storage;

FIG. 9 b contains two charts for Nov. 6, 1996, the top chart showing theamount of energy in storage over time, and the bottom chart showing thepressure and temperature curves in storage;

FIG. 10 is a chart showing the daily delivery schedules for the threedays, indicating the number of immediate use and energy storagewindmills that were operational, based on the settings of the hybridstations, and the number of storage tanks used and the cost ofgenerating the power each day;

FIG. 11 represents a first method of the present invention wherein alimited number of substantially constant power output periods arescheduled each day; and

FIG. 12 represents a second method of the present invention wherein alimited number of substantially constant power output periods arescheduled each day.

DETAILED DESCRIPTION OF THE INVENTION

The present application incorporates by reference the subject matter ofU.S. application Ser. No. 10/263,848, filed on Oct. 4, 2002, entitled“Method and Apparatus for Using Wind Turbines to Generate and SupplyUninterrupted Power to Locations Remote from the Power Grid,” whichdiscusses the windmill stations, storage, heating and other apparatusesand methods that are capable of being used with the present invention.The present application also incorporates by reference the subjectmatter of U.S. application Ser. No. 10/857,009, filed by applicants onJun. 1, 2004, 2003, entitled “A Method of Storing and Transporting WindGenerated Energy Using a Pipeline System,” which discusses the use of apipeline system for storing and transporting wind generated energy thatis capable of being used in connection with the present invention.

The apparatus portion of the present invention preferably comprisesdifferent types of windmill stations, including a first type having ahorizontal axis wind turbine that converts rotational mechanical powerto electrical energy using an electrical generator and providing energyfor immediate use (hereinafter referred to as “immediate use stations”),a second type having a horizontal axis wind turbine that convertsmechanical rotational power to compressed air energy for energy storage(hereinafter referred to as “energy storage stations”), and a third typethat combines the characteristics of the first two in a single windmillstation having the ability to convert mechanical rotational power toelectrical energy for immediate use and/or energy storage (hereinafterreferred to as “hybrid stations”). The present system is preferablydesigned to use and coordinate at least one of these different types ofwindmill stations so that a predetermined portion of the wind generatedenergy can be dedicated to energy storage and/or for immediate use.Systems that use compressed air to drive pneumatic tools and devices,without converting energy into electricity first (for both immediate useand storage), and those using other forms of storage, such as pipelines,batteries, hydraulic pressure, etc., are also contemplated.

The following discussion describes each of the three preferred types ofwindmill stations, followed by a description of how to coordinate thewindmill stations for any given application:

A. Immediate Use Stations:

FIG. 1 a shows a schematic flow diagram of a preferred immediate usestation. The diagram shows how mechanical rotational power generated bya windmill is converted to electrical power and supplied as electricalenergy for immediate use. Energy derived from the wind can be convertedto electrical power more efficiently when the conversion is direct,e.g., the efficiency of wind generated energy systems can be enhanced bydirectly harnessing the mechanical rotational movement caused by thewind as it blows onto the windmill blades to directly generateelectricity.

Like conventional windmill devices used for creating electrical energy,the present invention contemplates that each immediate use station willcomprise a windmill tower with a horizontal axis wind turbine locatedthereon. The tower is preferably erected to position the wind turbine ata predetermined height, and each wind turbine is preferably “aimed”toward the wind to maximize the wind intercept area, as well as the windpower conversion efficiency of the station. A wind turbine, such asthose made by various standard manufacturers, can be installed at thetop of the tower, with the windmill blades or fans positioned about ahorizontally oriented rotational shaft.

In this embodiment, a gearbox and an electrical generator are preferablylocated in the nacelle of the windmill such that the mechanicalrotational power of the shaft can directly drive the generator toproduce electrical energy. By locating the electrical generator directlyon the shaft via a gearbox, mechanical power can be more efficientlyconverted to electrical power. The electrical energy can then betransmitted down the tower via a power line, which can be connected toother lines or cables that feed power from the immediate use station tothe grid or other user.

In other embodiments, the wind energy can be converted to other forms ofenergy, depending on the end user requirements. For example, to power anindustrial park having pneumatic tools and equipment, compressors can beprovided to convert the wind energy from the windmill stations intocompressed air energy, which can then be used immediately by theindustrial park. This can be done by using the electricity generated bythe generator to drive the compressors, or, preferably, the mechanicalenergy from the windmills can be harnessed directly to operate thecompressors, in which case, the actual windmill tower can be set up likethe energy storage windmill towers described below.

The present invention contemplates that the immediate use stations areto be used in connection with other windmill stations that are capableof storing wind energy for later use as described in more detail below.This is because, as discussed above, the wind is generally unreliableand unpredictable, and therefore, having only immediate use stations tosupply energy for immediate use will not allow the system to be used toprovide power output at a constant rate. Accordingly, the presentinvention contemplates that in wind farm applications where multiplewindmill stations are installed, at least one energy storage stationwould preferably be installed and used.

B. Energy Storage Stations.

FIG. 1 b shows a schematic flow chart of an energy storage windmillstation. This station preferably comprises a conventional windmill towerand horizontal axis wind turbine as discussed above in connection withthe immediate use stations. Likewise, the wind turbine is preferablylocated at the top of the windmill tower and capable of being aimedtoward the wind as in the previous design. A rotational shaft is alsoextended from the wind turbine for conveying power.

Unlike the previous design, however, in this embodiment, energy derivedfrom the wind is preferably extracted at the base of the windmill towerfor energy storage. As shown in FIG. 1 b, a first gearbox is preferablylocated adjacent the wind turbine in the nacelle of the windmill, whichcan transfer the rotational movement of the horizontal drive shaft to avertical shaft extending down the windmill tower. In the preferredembodiment, at the base of the tower, there is preferably a secondgearbox designed to transfer the rotational movement of the verticalshaft to another horizontal shaft located on the ground, which is thenconnected to a compressor. The mechanical rotational power from the windturbine on top of the tower can, therefore, be transferred down thetower, and converted directly to compressed air energy, via thecompressor located at the base of the tower or somewhere nearby. Amechanical motor in the compressor forces compressed air energy into oneor more high pressure storage tanks or pipeline system located on theground. With this arrangement, each energy storage station is able toconvert mechanical wind power directly to compressed air energy, whichcan be stored for later use, such as during peak demand periods, and/orwhen little or no wind is available. In other embodiments, the energycan be stored in other storage means, such as batteries, hydraulicpressure, pipelines, etc. When batteries are used, the windmill towercan be set up like the immediate use windmill towers described above.

In another embodiment, the compressor is preferably located in thenacelle of the wind turbine and has mechanical gears associated with thewind turbine generator to produce compressed air energy using windenergy. The compressed air generated by the compressor is thenpreferably transmitted through a vertical pipe extending down the towerand into an associated compressed air storage means, such as a tank orpipeline, without converting the compressed air into electricity first.This avoids switching the energy back and forth between types which canresult in losses and therefore inefficient use of energy. This is auseful configuration such as in the case of using a turbo compressor andturbo expander to deliver compressed air energy at the end user sitewithout converting the wind energy to electrical energy first.

The energy storage portion of the present system preferably comprisesmeans for storing the compressed air energy, such as in storage tanks ora pipeline system. Reference can be made to U.S. application Ser. No.10/263,848, filed on Oct. 4, 2002, for additional information regardingthe storage tank, heating and other apparatuses and methods that arecapable of being used in connection with the present invention, and toU.S. application Ser. No. 10/857,009, filed on Jun. 1, 2004, entitled “AMethod of Storing and Transporting Wind Generated Energy Using aPipeline System,” for additional information regarding the pipelinesystem for storing and transporting wind generated energy which can beused in connection with the present invention. The storage facility ispreferably located in proximity to the energy storage stations, suchthat compressed air can be conveyed into storage without significantpressure losses.

Various size storage facilities can be used. The present systemcontemplates that the sizing of the storage facilities can be based oncalculations relating to a number of factors. For example, as will bediscussed, the volume size of the storage facility can depend on thenumber and ratio of energy storage and immediate use stations that areinstalled, as well as other factors, such as the size and capacity ofthe selected wind turbines, the capacity of the selected compressors,the availability of wind, the extent of the energy demand, etc.

When applicable, any of the many conventional means of converting thecompressed air into electrical energy can be used. In the preferredembodiment, one or more turbo-expanders are used to release thecompressed air from storage to create a high velocity airflow that canbe used to power a generator to create electrical energy. Thiselectricity can then be used to supplement the energy supplied by theimmediate use stations. Whenever stored wind energy is needed, thesystem is designed to allow compressed air in storage to be releasedthrough the turbo-expanders. As shown in FIG. 1 b, the turbo-expanderspreferably feed energy to an alternator, which is connected to an AC toDC converter, followed by a DC to AC inverter, and then followed by aconditioner to match impedances to the user circuits. Again, in otherembodiments, the compressed air energy may not need to be converted intoelectricity, i.e., the compressed air energy can be released asnecessary to drive pneumatic tools and equipment at an industrial parkor facility. It can also be released to produce super chilled air, whichcan then be used in an HVAC system.

The present invention preferably contemplates that the storagefacilities be designed to absorb and release heat to maintain the storedair at a relatively stable temperature, even during compression andexpansion. For example, when large storage tanks are used, the preferredembodiment preferably comprises using a heat transfer system made ofthin walled tubing extending through the inside of each tank, whereinheat transfer fluid (such as an antifreeze) can be distributed throughthe tubing to provide a cost-efficient way to keep the temperature inthe tank relatively stable. The tubing preferably comprisesapproximately 1% of the total area inside the tank, and is preferablymade of copper or carbon steel material. They also preferably contain anantifreeze fluid that can be distributed throughout the inside of thestorage tank, wherein the tubing acts as a heat exchanger, which is partof the thermal inertia system. The storage tanks are preferably lined byinsulation to prevent heat loss from inside.

The present system can also incorporate other heating systems, includingheating devices that can be provided on top and inside the storage tanksthat can help generate additional heat and pressure energy, and providea means by which the expanding air can be prevented from freezing. Insome cases, although not in the preferred system, the present inventioncan use a combination of solar heat, waste heat from the compressor,combustors, low-level fossil fuel power, etc., to provide the necessaryheat to increase the temperature and pressure of the compressed air inthe storage tank. In the pipeline storage embodiment, the pipeline canbe laid onto the floor of a desert, and painted black, such that itabsorbs the heat from the sun.

The present system also contemplates that the cold air created by theexpansion of the compressed air exhausting from the turbo-expander canbe used for additional refrigeration and HVAC purposes, i.e., such asduring the summer where air conditioning services might be in demand.

C. Hybrid Stations:

FIG. 2 a shows a hybrid station. The hybrid station is essentially asingle windmill station that comprises certain elements of the immediateuse and energy storage stations, with a splitting mechanism that allowsthe wind power to be allocated between power for immediate use andenergy for storage, depending on the needs of the system.

Like the two stations discussed above, a conventional windmill tower ispreferably erected with a conventional horizontal axis wind turbinelocated thereon. The wind turbine preferably comprises a horizontalrotational shaft having the ability to convey mechanical power directlyto the converters.

Like the energy storage station, the hybrid station is preferablyadapted so that wind energy can be extracted at the base of the windmilltower. As schematically shown in FIG. 2 a, the wind turbine preferablyhas a rotational drive shaft connected to a first gearbox located in thenacelle of the windmill, wherein horizontal rotational movement of theshaft can be transferred to a vertical shaft extending down the tower.At the base of the tower, there is preferably a second gearbox designedto transfer the rotational movement of the vertical shaft to anotherhorizontal shaft located at the base.

At this point, as shown in FIG. 2 a, a mechanical power splitter can beprovided. The splitter, which will be described in more detail below, isdesigned to split the mechanical rotational power of the lowerhorizontal shaft, so that an appropriate amount of wind power can betransmitted to the desired downstream converter, i.e., it can beadjusted to send power to an electrical generator for immediate use,and/or a compressor for energy storage.

Downstream from the mechanical splitter, the hybrid station preferablyhas, on one hand, a mechanical connection to an electrical generator,and, on the other hand, a mechanical connection to a compressor. Whenthe mechanical splitter is switched fully to the electrical generator,the mechanical rotational power from the lower horizontal shaft istransmitted directly to the generator via a geared shaft. This enablesthe generator to efficiently and directly convert mechanical power toelectrical energy, and for the electrical power to be transmitted to theuser for immediate use.

On the other hand, when the mechanical splitter is switched fully to thecompressor, the mechanical rotational power from the lower horizontalshaft is transmitted directly to a compressor, to enable compressed airenergy to be stored, such as in a high-pressure storage tank. Thisportion of the hybrid station is preferably substantially similar to thecomponents of the energy storage station, insofar as the mechanicalpower generated by the hybrid station is intended to be directlyconverted to compressed air energy, wherein the stored energy can bereleased at the appropriate time, via one or more turbo-expanders. Likethe previous embodiment, a high-pressure storage tank or pipeline systemis preferably located in close proximity to the windmill station so thatcompressed air energy can be efficiently stored in the tank for lateruse.

In an alternate embodiment, both a compressor and electrical generatorcan be located in the nacelle of the wind turbine. A switch or splittercan then be provided which apportions the rotational energy produced bythe wind to the compressor or generator or both. This can be done with aswitch that either connects or disconnects the compressor and generatorto the wind turbine's power, or apportions a predetermined amount ofenergy to both, such as by using a mechanical gear system similar to theone described below.

As will be discussed, the hybrid stations are preferably incorporatedinto large wind farm applications, and installed along with otherstations for immediate use and energy storage. In such case, thecompressor on each hybrid station can be connected to centrally locatedstorage facilities or a pipeline, such that a plurality of energystorage and hybrid stations can feed compressed air into them. In fact,the system can be designed so that all of the hybrid stations and theenergy storage stations can be connected to a single energy storagefacility or pipeline.

The mechanical power splitter, which is adapted to split the mechanicalpower between power dedicated for immediate use and power dedicated forenergy storage, and can comprise multiple gears and clutches so thatmechanical energy can be conveyed directly to the converters, whether acompressor or generator. In one embodiment, the mechanical splittercomprises a large gear attached to the lower horizontal drive shaftextending from the bottom of the station, in combination with additionaldrive gears capable of engaging and meshing with the large gear. A firstclutch preferably controls each of the additional drive gears to movethem from a first position that engages (and meshes with) the largegear, to a second position that causes them not to engage the largegear, and vice verse. This way, by operation of the first clutch, anappropriate number of additional drive gears can be made to engage (andmesh with) the large gear, depending on the desired distribution ofmechanical power from the lower drive shaft to the converters.

For example, one system can have one large gear and five additionaldrive gears, wherein the first clutch can be used to enable the largegear to engage, at any one time, one, two, three, four or five of theadditional drive gears. In this manner, the first clutch can control howmany of the additional drive gears are activated and therefore capableof being driven by the large gear (which is driven by the horizontaldrive shaft), to determine the ratio of mechanical power to be conveyedto the appropriate energy converter. That is, if all five additionaldrive gears are engaged with the large gear, each of the five additionaldrive gears will be capable of conveying one-fifth or 20% of the overallmechanical power to the energy converters. If only three of theadditional drive gears are engaged with the large gear, then eachengaged additional drive gear will convey one-third or 33.33% of themechanical power generated by the windmill. If two drive gears engagethe large gear, each will convey one half or 50% of the transmittedpower, etc.

The mechanical splitter of the present invention preferably has a secondclutch to enable each of the additional drive gears to be connecteddownstream to either an electrical, generator (which generates energyfor immediate use) or an air compressor (which generates compressed airenergy for energy storage). By adjusting the second clutch, therefore,the mechanical power conveyed from the large gear to any of theadditional drive gears can be directed to either the electricalgenerator or compressor. This enables the amount of mechanical powersupplied by the windmill station to be distributed and allocated betweenimmediate use and energy storage on an individual, customized andadjustable basis. That is, the amount of power distributed to each typeof energy converter can be made dependent on the adjustments that aremade by the two clutches, which determine how many additional drivegears engage the large gear, and to which energy converter each engagedadditional drive gear is connected. Those connected to the electricalgenerator will generate energy for immediate use, and those connected tothe compressor will generate energy for storage.

Based on the above, it can be seen that by adjusting the two clutches ofthe mechanical power splitter mechanism, the extent to which energy isdedicated for immediate use and energy storage can be adjusted andallocated. For example, if it is desired that 40% of the mechanicalpower be distributed to energy for immediate use, and 60% of themechanical power be distributed to energy for storage, the first clutchcan be used to cause all five of the additional drive gears to beengaged with the large gear, while at the same time, the second clutchcan be used to cause two of the five additional drive gears (eachproviding 20% of the power or 40% total) to be connected to theelectrical generator, and three of the five additional drive gears (eachproviding 20% of the power or 60% total) to be connected to thecompressor. This way, the mechanical splitter can divide and distributethe mechanical power between immediate use and energy storage at apredetermined ratio of 40/60, respectively.

In another example, using the same system, if it is desired that all ofthe mechanical power be distributed to immediate use, the first clutchcan be used to cause the large gear to engage only one of the additionaldrive gears, and the second clutch can be used to connect the oneengaged additional drive gear to the electrical generator, i.e., so thatall of the mechanical power generated by the windmill station will beconveyed for immediate use. Likewise, if it is desired that all of themechanical power be distributed to energy storage, the second clutch canbe used to connect the one engaged additional drive gear to thecompressor, i.e., so that all of the mechanical power generated by thewindmill station will be conveyed for storage.

The present system contemplates that any number of additional drivegears can be provided to vary the extent to which the mechanical powercan be split. It is contemplated, however, that having five additionaldrive gears would likely provide enough flexibility to enable the hybridstation to be workable in most situations. With five additional drivegears, the following ratios can be provided: 50/50, 33.33/66.66,66.66/33.33, 20/80, 40/60, 60/40, 80/20, 100/0, and 0/100.

By using the clutches on the mechanical power splitter, each hybridstation can be adjusted at different times of the day to supply adifferent ratio of power between immediate use and energy storage. Aswill be discussed, depending upon the power demand and wind availabilityforecasts, it is contemplated that different ratios may be necessary toprovide a constant amount of power to the user for extended periods oftime, despite unreliable and unpredictable wind conditions. This systemis designed to enable those ratios to be easily accommodated.

Other systems for splitting power are also contemplated. For example,when a system that drives only pneumatic tools and equipment iscontemplated, the hybrid stations can be adapted to supply compressedair energy without having to convert any of the energy into electricity.In such case, the system can be adapted to route the mechanical energyfrom the windmill stations to one or more compressors, wherein theenergy can be converted into compressed air energy, and then usedimmediately and/or stored first. In the case of a hybrid station, asplitter can be adapted to divert the mechanical energy to two differentcompressors, one compressor used to generate compressed air energy forimmediate use (such as at an industrial park or facility), and anothercompressor to generate compressed air energy into storage (for later useby the same industrial park or facility). Likewise, a splitter can belocated down stream from a single compressor, wherein a portion of thecompressed air energy can be split, i.e., some diverted and usedimmediately, and some stored for later use. This can be done with a Ysplitter in the pipeline, for example, or a splitter with a valve thatcontrols how much compressed air energy travels in each direction.

D. Control and Valve Mechanism:

The present system preferably comprises a system to control theoperation of the windmill stations, the clutches on the hybrid stations,the amount of energy or compressed air being fed into and out ofstorage, the operation of the compressors and generators, the operationof the turbo-expanders, etc. The control system is preferably able toset the total number of windmill stations that are to be in operation atany given time, including how many immediate use stations are operated,how many energy storage stations are operated, and how many hybridstations are operating in immediate use mode, and how many are operatingin energy storage mode. This way, at any given time, the total amount ofenergy to be supplied by the system, and how the energy is allocatedbetween immediate use and energy storage, can be accurately controlledand adjusted.

For example, if a system has a total of 50 windmill stations, with 20immediate use, 20 energy storage, and 10 hybrid stations, the operatorcan determine how many stations will be dedicated for immediate use, onone hand, and storage, on the other hand, by using the control system todetermine how many of the immediate use and energy storage stations willbe in operation, and how many of the hybrid stations will be set toeither immediate use or energy storage mode. For example, if it isdetermined that power from 28 immediate use windmill stations are neededfor a particular period, the system can run all 20 of the immediate usestations, and convert 8 of the 10 hybrid stations to immediate use mode.At the same time, if only 16 of the energy storage stations are neededduring the same period, 16 of them can be placed in operation, and theother 4 can be shut down, or the energy supplied by them can bedisconnected or vented.

The control system is also preferably designed to be able to maintainthe level of energy or compressed air energy in storage at anappropriate level, by regulating the flow of energy or compressed airinto and out of storage. Compressed air is introduced into storage viacompressors, and released from storage, such as via turbo-expanders.

On the releasing end, a valve system, like the one shown in FIG. 2 b,can be provided to allow a predetermined amount of compressed air to bereleased, such as through the turbo-expanders at any given moment. FIG.2 b shows an example of a storage tank with three couplings attached tothree turbo-expanders, wherein valves can be used to allocate anappropriate amount of air through the turbo-expanders. The chart shows 5different valve sequences, each associated with a particular pressureamount in the storage tank.

Valve sequence A is suited for 600 psig. According to this sequence,only valve numbers 3 and 5 are closed, and all others are open. In thismanner, air flowing through valve 1 enters into the firstturbo-expander, and can be converted to electrical energy, via the firstalternator. Also, because valves 2 and 4 are open, some of thecompressed air enters into the second and third turbo-expanders, and canbe converted to electrical energy via the second and third alternators.Because valves 3 and 5 are closed, only air flowing through valve 1 isused. In certain embodiments, the compressed air energy can be releasedto drive pneumatic equipment, wherein the turbo-expanders would not berequired to convert energy into electricity.

Valve sequence B is suited for 300 psig. According to this sequence,only valve 3 is open, and the other release valves, i.e., 1 and 5, areclosed. In this manner, air flowing through valve 3 enters into thesecond turbo-expander, and can be converted to electrical energy via thesecond alternator. Also, because valve 4 is open and valve 2 is closed,some of the compressed air can enter the third turbo-expander, and beconverted to electrical energy via the third alternator. The firstalternator remains unused because valves 1 and 2 are closed.

Valve sequence C is suited for 100 psig. According to this sequence,only one valve, i.e., number 5, is open. In this manner, air flowingthrough valve 5 enters into the third turbo-expander, and can beconverted to electrical energy via the third alternator. The first andsecond turbo-expanders and alternators remain unused.

When there is no pressure in the tank (see valve sequence D), the valvesare closed, in which case compressed air energy introduced into the tankfrom the compressors can build up over time, to help increase pressurein the tank. Similar controls are preferably used in connection with thecompressors to enable the tank to be filled, i.e., to determine the rateat which compressed air will enter into storage via the compressors. Thecontrols preferably enable the amount of pressure in the tank to bemaintained and moderated. A pipeline can also be used.

The controls can also be used to operate the heat exchangers that areused to help control the temperature of the air in the tank. Thecontrols determine which heat exchangers are to be used at any giventime, and how much heat they should provide to the compressed air in thestorage tanks.

The control system preferably has a microprocessor that ispre-programmed so that the system can be run automatically, based on theinput data provided for the system, as will be discussed. The presentinvention contemplates that an overall system comprising immediate use,energy storage and hybrid stations can be developed and installed,wherein depending on the demands that are placed on the system by thearea of intended use, a predetermined number of immediate use, energystorage and hybrid stations, can be in operation at any one time. Thisenables the present system to be customized and adapted to accommodatevarious wind forecasts during different times of the year, where windconditions can vary significantly.

E. Method:

The present method will now be discussed using an example, based onactual wind conditions found at a site in Kansas during November of 1996provided by Kansas Wind Power LLC. This period was selected because itcontained wind histories that were varied enough to show how the presentmethod can be applied in different circumstances.

FIG. 3 shows what is commonly called a wind histogram for the site. Thischart represents an actual wind history taken at an actual location. Ingeneral, this chart shows the average number of times or occurrences thewind reached a certain speed (when measured at hourly intervals) duringthe month of November 1996. The wind history is designed to enable astudy to be made of the average wind speeds at any given location,during any given time, from one season of the year to another.

This information can be useful, for example, in helping to formulate asolution for the entire year, which can be based on the best and worstcase scenarios presented by the studies. FIG. 3 shows that the peaknumber of occurrences for any particular wind speed measurement wasabout 43, which occurred when the wind velocity reached about 9 metersper second. Stated differently, during the month of November, whenmeasured every hour, the wind speed was about 9 meters per second moreoften than it was at any other speed, i.e., for a time estimated toequal about 43 hours (43 occurrences multiplied by one hour intervalsequals 43 hours). Another way to look at this is that the wind wasblowing an average of about 9 meters per second during an average ofabout 43 measurements taken at hourly intervals during the month.

The chart also shows that the wind speed was below 2 meters per secondfor only a few occurrences during the month. Likewise, the chart showsthat the wind speed was above 18 meters per second maybe once. Stateddifferently, what the chart shows is that the wind blew at below 2meters per second and above 18 meters per second for only a few hoursduring the entire month of November, which is helpful in determining theproper equipment and method to be used in connection with the site.

What this also means is that depending on what kind of wind turbines areselected, the chart can predict the amount of time that the windturbines would be operational and functional during the month to produceenergy. For example, if it is assumed that the wind turbines that areselected are designed to operate only when the wind speed is between 3meters per second and 15 meters per second, due to efficiency and safetyreasons, it can be predicted that during any given day during the monthof November those wind turbines would be operational for most, but notall, of the time.

In an actual application, more than one month will have to beinvestigated and studied. Indeed, such a determination generallycomprises a cost verses benefit analysis, and energy efficiency study,that takes into account the availability of wind during the worst andbest case scenarios over the course of an entire year, and the demandsthat are likely to be placed on the system at that location year round.

The amount of wind generated power produced by the wind turbines duringthe above mentioned period will then depend on the wind speed at anygiven time during the period. In general, the wind power to be derivedby a wind turbine is assumed to follow the equation:P=C ₁*0.5*Rho*A*U ³Where

-   -   C₁=Constant (which is obtained by matching the calculated power        with the dimensions of the wind turbine area and wind speed        performance)    -   Rho=Density of air    -   A=Area swept by wind turbine rotors    -   U=Wind Speed        This means that the amount of wind power generated by the wind        is proportional to the cube of the wind speed. Accordingly, in a        situation where the wind turbines are fully operational within        the velocity range between 2 meters per second and 18 meters per        second, the total amount of wind power that can be generated        will be a direct function of the total wind speed between those        ranges.

On the other hand, various wind turbines are designed so that the windpower output remains relatively constant during certain high windvelocity ranges. This can result from the windmill blades becomingfeathered at speeds above a certain maximum. For example, certain windturbines may function in a manner where within a certain velocity range,i.e., between 13 and 20 meters per second, the wind power generatedremains constant despite changes in wind speed. Accordingly, in theabove example, during a period where the wind speed is between 13 metersand 18 meters per second, the amount of wind power generated by the windturbine would be equal to the power generated when the wind speed is 13meters per second. Moreover, many wind turbines are designed so thatwhen the wind speed exceeds a maximum limit, such as 15 meters persecond, the wind turbines will shut down completely, to prevent damagedue to excess wind speeds. Accordingly, the total amount of energy thatcan be generated by a particular windmill should take these factors intoconsideration.

FIG. 3 also compares the actual number of occurrences with averagesdetermined by the Weibull distribution over a period of time. In thisrespect, it should be noted that wind histograms for wind speeds aretypically statistically described by the Weibull distribution. Windturbine manufacturers have used the Weibull Distribution associationwith the “width parameter” of k=2.0, although there are sites whereinthe width parameter has attained a value as high as k=2.52.

While it is desirable to know how often, on the average, certain windspeeds actually occur during the year, it is also important for purposesof the present invention to know when the various wind speeds will occurduring the day, i.e., forecasted on a daily basis, and the magnitude ofthose wind speeds, so that they can be used to formulate daily energydelivery schedules, which is one of the goals of the present invention.To develop a system that can be applied on a daily basis, it isnecessary to obtain daily wind speed forecasts and predictions inadvance of the upcoming day, to enable a plan or schedule to beestablished which can be applied the next day.

In this respect, FIG. 4 shows daily wind histories that have occurredduring a particular week in the same November time frame at the samesite. FIG. 4 shows a compilation of measurements taken over a periodextending from Nov. 1, 1996 to Nov. 6, 1996. This particular chart showsthe wind speeds that were measured at hourly intervals throughout eachday during that period.

The line that represents November 1, for example, starts after midnightwith the wind blowing slightly under 7 meters per second and ends atbefore midnight with the wind blowing slightly under 8 meters persecond. During that day, the wind fluctuated very little, with some ofthe lowest measurements, of about 4 meters per second, occurring in themorning hours, with a peak (spike) of about 7 meters per secondoccurring at about 2:00 p.m. The wind speeds then increased towardmidnight.

The line that represents November 2, on the other hand, shows the windto be more varied. The wind starts just after midnight at slightly below8 meters per second, and begins to slow down to a low of about 2 metersper second at about 10:00 a.m. and continues at a low level. Thenbeginning at about 5:00 p.m., the wind starts to pick up, ending the daywith wind speeds of close to 13 meters per second by midnight.

The next day, November 3, the wind continues to stay relatively high,while fluctuating up and down, reaching a low of about 9 meters persecond at about 8 a.m., and reaching a peak of about 15 meters persecond at about 1 p.m. On this day, the wind began after midnight atslightly below 13 meters per second, and ended with wind speeds ofslightly below 11 meters per second by midnight.

On November 4, the wind continues to fluctuate, reaching a peak of about13 meters per second, but begins to subside, reaching a speed of about 5meters per second by midnight.

On November 5, the day begins shortly after midnight with winds reachingas low as 2 meters per second, but then begins to increase dramatically,with winds reaching a peak of about 14 meters per second by about 4 p.m.The wind speed continues to stay relatively high and reaches about 12meters per second at midnight.

On the next day, the wind fluctuates again, reaching another peak ofabout 14 meters per second at about noon, and then begins to subside,reaching a low of about 7 meters per second by midnight.

What this chart tracks are the wind speeds that actually occurred duringthe first week of November 1996 at the site. In the present invention,however, wind speed forecasts are obtained for a particular site, sothat each day's anticipated wind speeds are predicted at least one dayin advance. That is, while FIG. 4 shows examples of wind histories, thepresent invention contemplates using wind speed forecasts, which aresimilar in content to the histories, except that they are projectionsfor the future, not records of the past. Such forecasts can be developedfrom data obtained from weather bureaus and other data resources, andusing the latest weather forecasting technologies. The present inventioncontemplates that relatively accurate forecasts can be developed,particularly when made within 24 hours before the forecasted day.

Once the data is obtained, the wind speed forecasts that are similar tothe wind histories for the upcoming day are prepared, which can be usedto determine the daily power delivery schedules that should beimplemented to maintain a relatively constant power output level for thelongest possible periods during the upcoming 24 hour period. Again, theobjective is to deliver power to the user or power grid using a reducednumber of constant power output level periods per day, i.e., preferablythree or less, although up to about 7 or more can be acceptable as willbe discussed. This allows for the number of times that the deliveryoutput level will have to be changed to be minimized, thereby placingless stress and work on the switching mechanism.

For purposes of this example, three of the six days in November 1996,i.e., November 1, 5 and 6, have been chosen for their extreme variedwind speeds, which are helpful in showing various aspects of the presentmethod. Days where wind speeds vary greatly require the use of storedenergy to smooth the delivery of energy to the user or grid, whereasdays that have fewer wind speed variations typically do not. These threedays will be studied and plotted to show how the present method can beapplied to determine a daily delivery schedule that can satisfy thestated objectives.

Before discussing the development of the delivery schedules, it ispertinent to discuss the selection of the wind turbines, which willdetermine the power output capacity for each windmill station, andtherefore, play a role in the design of the daily delivery schedules. Inthis respect, it is important to note that the overall design of thewind farm, including the total number of windmill stations that are tobe installed, can be based on the criteria that have been explained inApplicants' previous application, which has been incorporated herein byreference. In the particular example shown here, Applicant has selectedthe Nordex N50/800 wind turbine, the performance of which is beingcompared to a computer model in FIG. 5. This product has been chosen forthis example, but any conventional wind turbine could have been used.The selected wind turbine has a 50 meter diameter blade, a 50 metertower height and a swept area of 1,964 square meters. It turns on at 3meters per second, and has a design wind speed of 14 meters per second.This size was selected because the power generation capacity is suitedfor large applications, such as 100 to 1,000 MW wind farms, while at thesame time, the product is small enough to be transported by truck andrail.

The example storage facility has also been designed with 62 storagetanks, each being 60 feet long and 10 feet in diameter, with a rating of600 psig. This allows for the use of standard off-the-shelf componentsand hardware, which can reduce the overall cost of installation. Thedesign takes into account the worst case scenarios, i.e., days where themost number of tanks are required, to determine the total number oftanks that are needed for the wind farm at the site under consideration.The pipeline system can similarly be designed with the appropriatestorage capacity, based on the size of the pipe, and its length.

The methodology applied in formulating a delivery schedule for eachupcoming day involves at least the following three design considerationsthat relate to how much energy is generated by the immediate usestations, and how much is generated by the energy storage stations(including the hybrid stations that have been converted to one or theother):

-   -   1. The peak pressure in storage should not exceed 600 psig;    -   2. At any moment in time, the pressure in storage should never        be less than 100 psig; and    -   3. Pressure in storage at the end of each day should equal or        exceed that at the beginning of each day, if possible.

Based on these considerations, an iterative process is preferably usedto determine how many of each type of windmill station should be inoperation at any moment in time. Using the methodologies discussed inthe previous application, and the concepts discussed herein, the designthat has been chosen for this example is as follows: 24 immediate usestations, 6 energy storage stations, and 19 hybrid stations. Thisenables the system to be adjusted within a range of between a maximum of43 immediate use windmills (24 immediate use stations and 19 hybridstations converted to immediate use), and a maximum of 25 energy storagewindmills (6 energy storage stations and 19 hybrid stations converted toenergy storage). In general, more immediate use stations are used whenthere are fewer variations in wind speed, and more energy storagestations are used when there are more variations in wind speed. Thesystem also has the ability to shut off or otherwise vent power from anyof the windmill stations so that the appropriate ratio between immediateuse and energy storage can be obtained at all times, if necessary.

FIG. 6 shows two different delivery schedules that have been developedfor a 24-hour period on Nov. 1, 1996. Both charts compare the constantoutput curve (shown by the two straight lines) with the wind/poweravailability curve. The difference between the two schedules relates tohow many immediate use and energy storage stations have been placed inoperation during the day. The first chart represents a system with asetting where 87% of the total wind generated power is delivered to theuser or grid directly from the immediate use stations, and 13% of thepower is processed through storage. The second chart represents asetting where 40% of the wind generated power is delivered to the useror grid from the immediate use stations, and 60% of the power isprocessed through storage.

In both examples, each delivery schedule has been developed to providetwo substantially constant power output periods, one lasting 20 hours,and the other lasting 4 hours. This was primarily based on the shape ofthe wind speed curve on that day, which shows that the wind speedfluctuated around 5 meters per second during the first 20 hours, andthen jumped to fluctuate around 7 meters per second during the last 4hours. For this reason, the schedule was designed to provide asubstantially constant energy output level of about 2,500 kW during thefirst 20 hour period, and a substantially constant energy output levelof about 5,000 kW during the last 4 hour period.

Setting the delivery schedule to provide relatively few substantiallyconstant power output level periods during each day enables the systemto avoid surges and swings that could otherwise adversely affect thesystem. Had only the immediate use stations been used, like in aconventional windmill system, the amount of energy supplied to the useror grid would have followed the peaks and valleys of the wind speedcurve, which had severe fluctuations and oscillations. In such case, asevere peak or spike of energy would have been delivered to the user orgrid at about 3 p.m., along with other fluctuations and oscillations,placing additional stress and strain on the power system. By using thepresent invention, on the other hand, it can be seen that the amount ofpower delivered to the grid was very predictable and constant over anextended period of time.

It can also be seen from FIG. 6 that the cost of supplying power usingthe first schedule was $0.033/kW-Hr, while the cost of the power usingthe second schedule was $0.051/kW-Hr. This is due to the inefficienciesassociated with having to obtain a greater percentage of the energy fromstorage than from the immediate use stations. For this reason, what thisshows it that it is usually desirable to use the schedule that reliesfor a greater percentage of the power on the immediate use stations thanon the energy storage stations. In alternate embodiments, such as wherethe compressed air energy does not have to be converted intoelectricity, the efficiencies of energy placed in storage will beincreased, wherein a proportionally less amount of energy would have tobe stored, when compared to energy used immediately, to maintain theappropriate balance between the energy used immediately and the energystored.

During the time that the system is in operation, in addition toselecting a schedule that relies as much on energy from immediate usethan from energy storage, it is also desirable to balance the energythat is in storage, by keeping a balance between the energy that isintroduced into storage, with the energy that is being extracted fromstorage, so that at the end of each day, the amount of energy in storageis no less than it was at the end of the previous day. Moreover, asdiscussed above, another consideration is to always maintain at least100 psig of pressure in storage, so that in case the wind conditions donot actually occur as predicted in the forecasts, there will besufficient energy left over that could be relied upon at a later time ifneeded. At the same time, it is also desirable not to have more than apredetermined amount of pressure in storage, in which case pressure mayhave to be vented and wasted.

The energy processed through storage involves the following threescenarios, which must be accounted for in the development of thedelivery schedule:

First, the system must be designed to account for periods when the inputlevel into storage is equal to the output. That is, if the constantdelivery power output level matches the rate at which power is beingsupplied from a combination of the immediate use and energy storagestations, then theoretically, the amount of energy in storage willremain substantially constant during these periods. Of course, this doesnot take into account certain inefficiencies, as well as waste heat fromthe compressor, and any of the heating devices discussed above.Nevertheless, it is clear that there will be times when the amount instorage will remain substantially constant. This can occur, for example,when no energy from storage is used, and all of the energy is obtainedfrom the immediate use stations, to maintain the constant power outputlevel.

Second, the system must be designed to account for periods when theinput level into storage is less than the output. During these periods,it can be seen that a greater percentage of energy will be extractedfrom storage, than will be provided into storage, to maintain a constantpower output level, in which case the amount of energy in storage can bereduced over time. While this can go on temporarily for a short periodof time, eventually, the delivery schedule would have to be adjusted sothat the energy in storage will be re-stored, to maintain the level ofenergy in storage in substantial equilibrium. In other words, thedelivery schedule must be adapted to factor in the potential for moreenergy being introduced back into storage later that day, in order forthe amount of energy in storage at the end of each day to equal orexceed the amount in storage at the beginning of each day.

Third, the system must be designed to account for periods when the inputlevel into storage is more than the output. In this case, energy will beintroduced into storage at a rate that is greater than that at which itis extracted. As discussed, this is important because of the secondscenario, where the energy in storage can otherwise become reduced. Inthis case, the delivery schedule must be adapted to account for thepossibility that during some periods a greater percentage of energy willbe introduced into storage than would be extracted from storage, suchthat the amount of energy in storage can be increased over time. At thepoint that the pressure becomes too high, however, the pressure willhave to be vented, and/or the compressors will have to be turned off.

The first chart in FIG. 7 a shows the two constant power output periods(one lasting 20 hours and the other lasting 4 hours) being compared tothe amount of energy that is being supplied into storage, which is shownby the up and down curve. It can be seen that there are severedifferences between these curves, which represent the second and thirdscenarios discussed above, i.e., periods where input exceeds output, oroutput exceeds input. As shown in the second chart of FIG. 7 a, thereare changes in the “wind stored” curve, which occur by virtue of theenergy level in storage being increased at times, and reduced at times,depending on which of the above scenarios apply at any moment in time.This chart shows that less than 1,000 kW of net power was supplied intostorage at any given time based on 87% of the power being supplieddirectly to the grid, and 13% of the power being processed throughstorage. The curvature of the “wind stored” line also shows that theamount of energy being supplied into storage can fluctuate over time.

FIG. 7 b shows the net energy accumulated into storage during the day,again, based on the occurrence of the three scenarios discussed above.It can be seen from the top chart in FIG. 7 b that the accumulatedenergy in storage fluctuates over the course of the day, which isnecessary for the power output levels to remain constant. It can also beseen in the bottom chart that the pressure level (shown by the topcurve) in storage drops to almost 100 psig at about 1:00 p.m. and thenagain between 6:00 and 8:00 p.m., which is a result of a combination ofthe three scenarios discussed above, where net energy being extractedmay exceed the net energy being supplied. It can also be seen that thedelivery schedules have been plotted successfully to ensure that thepressure never goes below 100 psig, and that an equal amount or moreenergy is in storage at the end of the day than at the beginning of theday. The pressure also never exceeds 600 psig.

In actual practice, since these delivery schedules will be based onprojected wind speed forecasts, the actual planning of the scheduleswill have to reflect a fairly conservative approach, to account for thepossibility that the actual wind conditions may not be as anticipated.If the schedules are not conservative, it may be possible that thepressures could fall below 100 psig or run out altogether, in which casethere will not be enough pressure in storage to supply power to the useror grid. If energy in storage does run out, the system will fail to beable to provide a constant power output level during those times, i.e.,wind speed fluctuations will continue to cause fluctuations in thedelivery of power output, since there will be no energy in storage tooffset and smooth the wind speed and power generation fluctuations fromthe immediate use stations. In such case, the delivery schedule willhave to be adjusted to make up for the loss of power in storage duringthe previous periods, which the present invention contemplates may benecessary at times. On the other hand, if the schedules are tooconservative, pressure in storage may have to be vented, in which caseenergy may be wasted.

FIGS. 8 a and 8 b, and 9 a and 9 b, show similar charts for the 24 hourperiods on Nov. 5 and 6, 1996, respectively.

FIG. 8 a shows a delivery schedule that has been developed for the24-hour period on Nov. 5, 1996, based on the wind history that occurredon that day. This chart represents a delivery schedule where 60% of thetotal wind generated power is delivered to the grid directly from theimmediate use stations, and 40% of the power is processed throughstorage. Because the wind speed curve on this day varied significantly,this delivery schedule was developed to provide seven different constantpower output periods, not two or three.

The first constant level period (from midnight to 3:00 a.m.) providesvery little if any power to the grid. This is mainly due to the factthat there was little or no wind during that time.

The second constant level period from 3:00 a.m. to 9:00 a.m. providesabout 4,000 kW, which is due to a slight increase in wind speedbeginning at about 4:00 a.m. The third constant level period extendsonly from 9:00 a.m. to 10:00 a.m. due to the sharp increase in windspeed that begins at about 8:00 a.m. This period is short because theincrease in wind speed is so dramatic that the output had to beincreased to 10,000 kW to efficiently use the energy being supplied andgenerated.

The fourth constant level period extends from 10:00 a.m. to 1:00 p.m.,at a level of about 24,000 kW, which reflects the increasing wind speedsduring that time. Because the wind speed continues to increase after1:00 p.m., and continues to blow at very high levels, the fifth constantlevel period is set at 35,000 kW and extends for nine hours from 1:00p.m. to 10:00 p.m. This is the period during which the power levels areconstant for the longest period during the day, wherein the outputlevels and therefore delivery of power to the grid are predictable andstable.

What happens at the end of the day, towards midnight, however, is thatthe wind speeds begin to drop off dramatically. Accordingly, the finaltwo hours of the day are broken up into two more constant power levelperiods, beginning with a level of about 32,000 kW from 10:00 p.m. to11:00 p.m., and then dropping significantly to about 10,000 kW from11:00 p.m. to midnight. While it is certainly more advantageous tocreate fewer constant level periods during each day, when consideringthe severe fluctuations and oscillations that have occurred during theday, it can be seen that the system was required to be adjusted morefrequently to provide the degree of predictability and stability thatwould be needed to provide the advantages discussed above. By using thepresent invention, the amount of power delivered to the grid was mademore predictable and constant for fixed periods during the day, eventhough there were more of those periods on this day than on November 1.

The second chart in FIG. 8 a shows the net energy being supplied intostorage during the day (shown by the grey line). This is based on having40% of the power from the windmill stations being introduced intostorage, while at the same time, a certain amount of energy beingextracted from storage at a rate necessary to maintain the overall poweroutput levels relatively constant. Again, the amount stored is based onthe accumulation of various conditions existing throughout the day,including the occurrence of the three scenarios discussed above.

It can be seen from the second chart in FIG. 8 a that the supply ofenergy into storage fluctuates over the course of the day, from arelatively small amount in the morning, to a relatively large amount inthe afternoon. Although a greater amount of power is delivered to theuser or grid during the afternoon hours, the immediate use stationsgenerate the bulk of that power. Accordingly, it can be seen that asignificant amount of energy is being supplied into storage during theafternoon hours, even though a significant amount of power, i.e., 35,000kW, is delivered to the grid at the same time.

The top chart in FIG. 8 b shows the accumulation of energy in storageduring that day, which increases substantially over time. This is due tothe significant amount of energy that is being introduced into storage,as shown in the bottom chart of FIG. 8 a. The top chart of FIG. 8 bshows the curve going from about 10,000 kW-hr to about 70,000 kW-hr overthe course of the 24 hour period.

The bottom chart shows that there are contributions being made to thetotal energy by virtue of the temperature and pressure levels increasingin storage as well. It also shows severe fluctuations in the amount ofpressure in storage, which is one of the reasons that seven differentconstant output level periods had to be scheduled on that day, to ensurethat the pressure never exceeded 600 psig, and never went below 100psig, although it can be seen that an excessive buildup of pressure instorage that exceeded 600 psig nevertheless occurred at about 1:00 p.m.

FIG. 9 a shows a delivery schedule that has been developed for the24-hour period on Nov. 6, 1996, based on the wind history that occurredon that day. This chart represents a delivery schedule where 50% of thetotal wind generated power is delivered to the user or grid directlyfrom the immediate use stations and 50% of the power is processedthrough storage. Because the wind speed curve on this day variedsignificantly, this delivery schedule was developed to provide sixdifferent constant power output periods, which, as discussed below, wasnecessary to maintain the pressure in storage between 100 psig and 600psig.

On this day, the amount of power remaining in storage from the previousday was relatively high, as discussed above, and the wind speeds wererelatively high during the early morning hours, and continued to be highthroughout the morning and into early afternoon, when it began to dropoff slightly. Accordingly, the delivery schedule shows a significantamount of power being delivered to the grid during the late morning andearly afternoon hours, with several incrementally increasing constantpower output periods extending from midnight the night before untilabout 2:00 p.m. For example, three constant level periods wereimplemented, including one from midnight until 3:00 a.m., wherein theenergy delivered was about 14,000 kW. In the other two periods, oneextended from 3:00 a.m. to 6:00 a.m., with about 27,000 kW of energybeing delivered, and another extended from 6:00 a.m. to 2:00 a.m., withabout 36,000 kW of energy being delivered during that period.

When the wind speeds began to drop off, however, the amount of powerscheduled to be delivered also dropped off. Three additional constantlevel periods were experienced, including one from 2:00 p.m. until 3:00p.m., where the energy delivered was about 18,000 kW, one from 3:00 p.m.to 4:00 p.m., with about 13,000 kW of energy being delivered, and thelast from 4:00 p.m. to midnight, with about 10,000 kW of energy beingdelivered. During this day, while the schedule called for six constantoutput level periods, two of the periods lasted for 8 hours each, whichprovided an extended period of 16 hours during which output levels wereconstant for an extended period of time.

The second chart in FIG. 9 a shows the net energy being supplied intostorage during the day (shown by the grey line), which is based onhaving 50% of the power from the windmill stations introduced intostorage. It can be seen that the supply of energy into storagefluctuates over the course of the day, starting with a relatively highlevel of energy being supplied during the morning hours when the windspeeds were high, to a relatively low level of energy being suppliedinto storage during the afternoon and evening hours when the wind speedsbegan to dissipate. In this case, the bulk of the power delivered to thegrid during the morning hours was generated by the immediate usestations, but a substantial amount of power was also being deliveredthrough storage, as the difference between the two curves show in thetop chart in FIG. 9 a.

The top chart in FIG. 9 b shows the accumulation of energy in storageduring the day, wherein the amount increases steadily over time. This isdue to the significant amount of energy being introduced into storage,as shown in the bottom chart of FIG. 9 a, particularly during themorning hours. The top chart of FIG. 9 b shows the curve going fromabout 0 kW-hr to about 90,000 kW-hr over the course of the 24 hourperiod. The bottom chart shows that there are contributions being madeto the total energy from the temperature and pressure increases, whichfluctuated substantially, in storage as well.

As can be seen in the bottom charts on FIGS. 8 a and 9 a, the pressurecurve fluctuated considerably during the two day period between Nov. 5and 6, 1996. These pressure curves are significant because they show howimportant it is to change the level of the constant level output periodsoccasionally to ensure that the pressures do not go below 100 psig, norabove 600 psig. As can be seen, the curve on several occasions, onNovember 6, went above the 600 psig level. In some circumstances, suchas when temperature levels are above 70 degrees F., it may bepermissible to increase the pressure to 800 psig, although the systemwould have to be designed with the appropriate storage facilities toensure that higher pressures can be handled by the system.

FIG. 10 shows how the delivery schedule was carried out using apredetermined number of immediate use, energy storage and hybridstations on any given day during the period. On each day, all of thewindmill stations were operational, but the ratio between the types ofstations that were used at any given moment was adjusted based on howmany hybrid stations were set to immediate use and energy storage. Forexample, on November 1, the total ratio used included 43 immediate usewindmills (including 24 immediate use stations and 19 hybrid stationsconverted to immediate use) and 6 energy storage stations. Thisaccounted for the 87% to 13% ratio discussed above.

On November 5, the ratio included 30 immediate use windmills (including24 immediate use stations and 6 hybrid stations converted to immediateuse) and 19 energy storage windmills (including 6 energy storagestations and 13 hybrid stations converted to energy storage). Thisaccounted for the 60% to 40% ratio discussed above.

On November 6, the ratio included 25 immediate use windmills (including24 immediate use stations and 1 hybrid station converted to immediateuse) and 24 energy storage windmills (including 6 energy storagestations and 18 hybrid stations converted to energy storage). Thisaccounted for the 50% to 50% ratio discussed above.

The chart also shows that the number of storage tanks required at anygiven moment will depend on the number of energy storage stations thatare operational. Also, the chart shows that over the course of a 20 yearperiod, the cost of the energy generated by these three differentdelivery schedules remains relatively constant, i.e., about $0.033kW-hr.

1. A method of coordinating and stabilizing the delivery of windgenerated power, comprising: producing compressed air energy using atleast one windmill station with a compressor capable of generatingcompressed air energy; storing said compressed air energy in a pipelinecapable of distributing said compressed air energy to a remote location;forecasting or obtaining a forecast of wind speed conditions at saidwindmill station and predicting the wind speed conditions and theresulting wind power availability levels for the upcoming period of timebased on the forecast; preparing an energy delivery schedule to theremote location based on the predictions for wind speed and wind poweravailability levels for the upcoming period of time, taking into accountthe amount of energy that can be stored and used at a later time; andsetting a reduced number of constant power output periods based on thedelivery schedule during the upcoming period of time, during which timeenergy delivery levels are substantially constant, despite fluctuationsand oscillations in wind speed and wind power availability levels. 2.The method of claim 1, wherein the upcoming period of time is the next24 hour period and the method comprises setting no more than sevenconstant power output periods during any given 24 hour period.
 3. Themethod of claim 1, wherein the method comprises providing apredetermined number of immediate use stations dedicated to providingenergy for immediate use, and a predetermined number of energy storagestations dedicated to storing energy for later use, and determining theratio between the number of immediate use and energy storage stationsthat are to be in operation during the upcoming period of time.
 4. Themethod of claim 3, wherein the delivery schedule determines the amountof energy that can be supplied directly from the immediate use stations,and the amount of energy that can be provided from storage from theenergy storage stations, and the amount of energy expected to be usedand withdrawn so as to maintain a predetermined amount of energy instorage.
 5. The method of claim 1, wherein the delivery schedule is setso that the amount of energy in storage from the energy storage stationsat the end of the upcoming period of time is equal to or greater thanthe amount of energy in storage at the beginning of the upcoming periodof time.
 6. The method of claim 1, wherein the delivery schedule is setso that the amount of pressure in storage at any given time will notexceed 600 psig or go below 100 psig.
 7. The method of claim 3, whereinthe method comprises providing a predetermined number of hybrid windmillstations dedicated to providing energy for immediate use and/or storage,and using the hybrid stations to supplement the number of stations thatare in operation.
 8. The method of claim 7, wherein the immediate usestations are adapted to supply electrical energy directly to the remotelocation, and the energy storage stations are adapted to provide energyinto storage, and the hybrid stations are adapted to switch betweenbeing an immediate use station to supply electrical energy directly, andan energy storage station to provide compressed air energy into storage.9. The method of claim 1, wherein said remote location is provided withpneumatically driven equipment, and the compressed air energy in saidpipeline is released at said remote location to drive said pneumaticallydriven equipment without having to convert the compressed air energyinto electricity first.